1. Field of Invention
The present invention relates generally to antioxidant analysis for solder plating solutions, and more specifically, to a system and method for determining the concentration of antioxidant in solder plating solutions.
2. Related Art
Solder plating solutions contain a variety of organic additives, which are important for improving the plating quality and preventing formation of solder bumps on the plate surface.
Antioxidant additive, such as catechol, is usually added into solder plating solutions, for preventing oxidation of the divalent tin (Sn2+) ions from being oxidized to tetravalent Sn4+ ions by oxygen dissolved in the solder plating solutions. It is necessary to monitor the concentration of such antioxidant additive in the solder plating solutions and to replenish such additive when it becomes depleted over time.
Currently, accurate, on-line analysis of the antioxidant (catechol) concentration in high-lead solder plating solutions is still impossible, due to the fact that the presence of lead, tin, and methane sulfonic acid (MSA) has a significant matrix effect on the measurement of the antioxidant concentration, i.e., concentration variations of lead, tin, and methane sulfonic acid affect the measurement results obtained for the antioxidant.
It is therefore an object of the present invention to provide a method for quick and accurate on-line analysis of the antioxidant concentration in solder plating solutions, which minimize the matrix effect from lead, tin, and methane sulfonic acid concentration variation.
Other objects and advantages will be more fully apparent from the ensuring disclosure and appended claims.